Glass strand is typically produced by attenuating filaments through orifices or tips at the bottom of a heated bushing containing molten glass. The filaments may be cooled by spraying them with water as they leave the bushing. The filaments are then passed across the application surface of an applicator where they are coated with a binder and/or size. The coated filaments are then gathered into strand form in a gathering shoe, which is typically a grooved wheel or cylinder formed of a material such as graphite. The strand may then be traversed across the face of a rotating spiral and wound as a forming package on a rotating collet carried by a winder. Alternatively, the strand from the gathering shoe may be passed between cutting blades and chopped into particulate glass fiber strands. In a further alternative, the strand may be attenuated by an attenuator, such as a belt or wheel attenuator, and collected in a container as a containerized package.
In each of the above operations, a significant amount of waste glass fiber strand is produced. In most of the above described operations inconsistent filament diameter results during start-up and slow down of the systems due to the fact that filament diameter is inversely proportional to the speed of attenuation for a given bushing.
Further, such occurrences as low speed attenuation during doffing of the forming package, restarting the strand formation process after a strand breakout, and the like are all examples of the formation of waste strand.
In the past, waste filaments were passed through the forming operation in the same manner as production quality filaments until they had passed the gathering shoe and were formed into strand. Only at this point were they segregated into waste. All of the waste strands and the filaments forming them had been coated with binder and/or size, just as the production quality filaments were coated. As the binder and/or size which has been coated onto the waste filaments cannot be recovered, when one realizes that waste strand may represent up to about 15 percent or more of the production of a typical glass fiber forming plant, it is obvious that the prior art strand formation methods consume a significant amount of binder and/or size which is in actuality being wasted. It is, therefore, desirable to substantially reduce the amount of binder and/or size which is wasted by being coated onto waste filaments.
A second problem encountered with the continual coating of filaments with binder and/or size occurs from the necessity of the forming level operator to manually handle the strands during such operations as start-up, and other occurrences of a glass fiber forming operation. To begin the winding of a new forming package on a collet, to begin the chopping of strand, to thread an attenuator, and to restart any of these devices after a strand breakout, the operator must manually feed the strand to the operation. This requires physical contact between the operator's skin and the coated strand. Some binders and/or sizes may have adverse dermatological effects on an operator's skin from the constant contact of the operator's hands with coated strands. It is also desirable, therefore, to reduce substantially or eliminate physical contact between the operator and glass strand having irritating binders and/or sizes coated thereon.
Concurrently filed U.S. application Ser. No. 775,483 filed Mar. 8, 1977 of David H. Griffiths and incorporated herein by reference discloses a method of reducing both binder and/or size waste and physical contact between the operator and the coated glass strands. Generally, the method comprises moving the filaments from the application surface of an applicator during the attenuation of waste filaments and their formation into waste strands while allowing the filaments to contact the application surface and become coated with the binder and/or size only during the formation of production quality strand. The present invention concerns apparatus for carrying out the aforementioned method.